<p>A heat roller, comprising a cylindrical sheet-like heating element having a resistance member buried in an insulation member, wherein the sheet-like heating element is disposed between an inner tube and an outer tube, the outer tube is formed longer than the inner tube so that the nonuniformity of heat in the heat roller can be reduced, and the coefficient of thermal expansion of the material of the outer tube is made larger than that of the material of the inner tube. A triple tube heat roller may be provided.</p>
